Systems and methods to determine seed layer thickness of trench sidewalls

ABSTRACT

One aspect of the present invention relates to a method to facilitate formation of seed layer portions on sidewall surfaces of a trench formed in a substrate. The method involves the steps of forming a conformal seed layer over a barrier layer disposed conformal to a trench, wherein the trench is formed in the substrate; reflecting a light beam of x-ray radiation at the seed layer sidewall portions; generating a measurement signal based on the reflected portion of the light beam; and determining a thickness of the sidewall portions based on the measurement signal while the sidewall portions are being formed over the trench.

TECHNICAL FIELD

The present invention generally relates to processing a semiconductorsubstrate. In particular, the present invention relates to a method ofdetermining whether seed layer thickness on trench sidewalls issufficient for desired circuit performance.

BACKGROUND ART

In the semiconductor industry, there is a continuing trend toward higherdevice densities. To achieve these high densities there has been andcontinues to be efforts toward scaling down the device dimensions onsemiconductor wafers (e.g., at submicron levels). In order to accomplishsuch high device packing density, smaller and smaller features sizes arerequired. This may include the width and spacing of interconnectinglines, spacing and diameter of contact holes and the surface geometrysuch as corners and edges of various features.

The requirement of small features with close spacing between adjacentfeatures requires high resolution photolithographic processes. Ingeneral, lithography refers to processes for pattern transfer betweenvarious media. It is a technique used for integrated circuit fabricationin which a silicon slice, the wafer, is coated uniformly with aradiation-sensitive film, the resist and an exposing source (such asoptical light, x-rays, etc.) illuminates selected areas of the surfacethrough an intervening master template, the mask, for a particularpattern. The lithographic coating is generally a radiation-sensitivecoating suitable for receiving a projected image of the subject pattern.Once the image is projected, it is indelibly formed in the coating. Theprojected image may be either a negative or a positive image of thesubject pattern. Exposure of the coating through a photomask causes theimage area to become either more or less soluble (depending on thecoating) in a particular solvent developer. The more soluble areas areremoved in the developing process to leave the pattern image in thecoating as less soluble polymer.

The ability to reduce the size of computer chips while increasingpacking densities and performance is driven by lithography technologyand metallization processes and is especially critical to ultra largescale integration (ULSI) circuits. ULSI circuits require responsivechanges in interconnection technology which is considered a verydemanding aspect of ULSI technology. High density demands for ULSIintegration require planarizing layers with minimal spacing betweenconductive lines and/or trenches.

Traditional methods of forming interconnection structures include theuse of photoresist patterning and chemical or plasma subtractive etchingas the primary metal technique. However, because the geometry ofsemiconductor circuits continues to decrease, traditionalinterconnection techniques are unsuitable. In particular, problemsassociated with traditional methods include trapping impurities orvolatile materials, such as aluminum chloride, in interwiring spaces(i.e., may pose reliability risk to device), leaving residual metalstringers (i.e., may cause electrical shorts) and poor step coverage.These problems contribute to low yields, poor performance, and lowerlayout densities. More recent developments in interconnect technologyhave improved, however, problems such as non-uniform seed layerdeposition and void formation within the seed layer still contribute topoor device performance and product yield losses. The seed layer iscommonly deposited or formed over a barrier layer for the purpose ofproviding a material on which a subsequently deposited material willreadily form. Therefore, seed layer coverage is critical to theformation and performance of the interconnect structure.

Therefore, there is an unmet need for a process to determine thesufficiency of seed layer coverage in the sidewall portions of a trench.

SUMMARY OF THE INVENTION

The present invention provides a system and a method for monitoringin-situ and controlling seed layer coverage throughout the surfaces of atrench. By monitoring the thickness of the seed layer duringsemiconductor processing, one or more process control parameters may beadjusted to help achieve a desired seed layer coverage. As a result, thenumber of process steps required to achieve the desired seed layercoverage may be reduced, providing a more efficient and economicalprocess.

One aspect of the present invention provides a semiconductor processingsystem. The system includes a processing chamber operable to form a seedlayer over a barrier layer conformal to a trench surface, particularlythe trench sidewalls, in the chamber. The barrier layer is formed overanother layer which includes a trench therein. An x-rayscattering/reflectometry system performs in-situ thickness measurementsof the seed layer being formed and provides a measurement signalindicative of the measured thickness. In accordance with another aspectof the present invention, the thickness of the seed layer may also bemonitored and controlled. A signature is then generated utilizing themeasurement signal and the signature is compared with a library ofsignatures to determine the thickness of the seed layer.

To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings. These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention will become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a high-level block representation of a system inaccordance with one aspect of the present invention.

FIG. 2 illustrates a high-level block diagram illustrating an example ofa measurement system employing x-ray reflectometry that may be utilizedin accordance with one aspect of the present invention.

FIG. 3 illustrates a high-level block diagram illustrating an example ofa measurement system employing x-ray reflectometry in accordance withone aspect of the present invention.

FIG. 4 illustrates a block diagram of program modules that reside in amemory system in accordance with one aspect of the present invention.

FIG. 5 illustrates a graph of exemplary x-ray reflectometry datacorresponding to the thickness of a seed layer in accordance with oneaspect of the present invention.

FIG. 6 illustrates a flow diagram illustrating a methodology formeasuring a thickness of a seed layer in accordance with one aspect ofthe present invention.

DISCLOSURE OF INVENTION

The present invention involves a system and a method for monitoringin-situ and controlling seed layer coverage throughout the surfaces of atrench. One aspect of the present invention generally relates to usingx-ray reflectometry to determine the sufficiency of seed layer coverageat the sidewall portions of a trench. In particular, x-ray reflectometrymay be employed to determine the thickness of the seed layer curing orafter it has formed on the side and bottom surfaces of the trench.Alternatively or in addition, a profile of the seed layer may bemeasured to determine sufficiency of sidewall coverage. The system andmethod mitigate void formation associated with insufficient seed layerdeposition within and over the surfaces of a trench (via) related toforming interconnect structures, capacitors, and the like.

The system and method employ a library of signatures which are stored ina memory. An x-ray beam is directed to the surface of a seed layer, andthe reflected beam is collected and analyzed. One or more signatures ofthe reflected x-ray beam can be generated and the one or more signaturesare compared to the signatures of the library, so as to determine theapproximate thickness of the seed layer. The thickness of the seed layercan be monitored and determined during or after its formation. Thesystem and method can be employed in-situ, so that the thickness of theseed layer can be monitored and controlled during fabrication of thedevice/feature. As a result, seed layer formation may be optimizedthereby mitigating product yield losses and ineffective performance ofthe device.

The present invention is to be described with reference to FIGS. 1-6below, wherein like reference numerals are used to refer to likeelements throughout. In the following description, for purposes ofexplanation, numerous specific details are set forth in order to providea thorough understanding of the present invention. It may be evident,however, to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownstructures and devices are shown in block diagram form in order tofacilitate description of the present invention.

Referring initially to FIG. 1, a system 10 for monitoring in-situ a seedlayer deposition process 12 throughout the sidewall portions of a trenchis shown. The system 10 may also facilitate measuring the thickness ofthe seed layer at the sidewall portions to determine substantialcoverage. The process 12, for example, includes deposition of a seedlayer (e.g., copper and copper alloys including copper-zinc,copper-aluminum, copper-zinc-aluminum, copper-nickel, copper-silver,copper-gold, copper-platinum and copper-paladium, or a combinationthereof) over a barrier layer (e.g., metallic nitride or metal), both ofwhich are formed over a layer or substrate having at least one trenchformed therein. The barrier layer and seed layer are conformal to thetrench surfaces (i.e., side and bottom surfaces).

The system 10 also includes a control system 14 for controllingoperating characteristics of the process 12. The operatingcharacteristics associated with the process 12 may include, for example,deposition enablement, temperature, concentration of gases within theprocess, pressure associated with the process, and timing parametersassociated with different steps in a multi-step fabrication process. Thecontrol system 14 may adjust one or more selected operating parametersof the process 12 based on sensed operating conditions associated withsuch process 12.

A measurement system 16 is operatively associated with the process 12 tomeasure in-situ thickness of the seed layer as it is being formed. Thatis, the measurement system 16 includes a thickness monitoring portion18, which may be located within or integrated into the process 12. Thethickness monitoring portion 18 may also include an enclosed processingchamber. The measurement system 16, for example, samples the thicknessof layers being formed on the substrate at one or more locations, suchas near the center and near one or more edge locations of the substrate.In particular, it may be desirable to obtain measurements from two ormore spaced-apart locations, such as the center and one or more edgepositions. Such measurements may enable a better determination as touniformity of the layer thickness, which in accordance with an aspect ofthe present invention, may be employed to adjust the fabrication processto achieve a desired level of uniformity of layer thickness.

The measurement system 16 may implement any known technique operable tomeasure the thickness of the layer formed in the process 12. Examples oftechniques that may be utilized in accordance with an aspect of thepresent invention include optical interference, x-ray reflectometry,capacitance and use of an associated color chart.Microprocessor-controlled optical interference (e.g.,microspectrophotometry) is a common type of optical measurementtechniques that could be employed.

The measurement system 16 is coupled to the control system 14 forproviding a signal indicative of the measured layer thickness beingformed in the process 12. The control system 14, for example, includes amemory (not shown) for storing each target layer thickness, which mayvary according to the process. The control system 14 also includes asignature generation system 16, which creates a signature from or basedon the signal measurements over a predetermined spectral range. Thecontrol system 14 also includes a signature library 22 that includeshundreds of thousands of signatures, each corresponding to a particulartype and thickness of seed layers. The signatures may also correspond toprofiles of trenches having desired seed layer coverage particularly atthe sidewall portions.

An analysis system 20 is provided for comparing the generated signaturewith signatures in the signature library 22. By examining a signaturelibrary 22 of reflectivity intensity/scattering angle signatures, adetermination can be made concerning the properties of the surface, suchas thickness of the layer being formed thereon. The control system 14 iscoupled to the process 12 and maybe programmed and/or configured tocompare the measured thickness relative to the target thickness anddetermine what action, if any, should be taken to drive the process 12so that a target thickness and/or a desired level of uniformity ofthickness may be achieved. The control system 14 is also coupled to anoutput device 24 which may be used to display results to a user.

The system 10 further may include one or more process sensors (notshown) for monitoring process operating conditions and providing anindication of such conditions to the control system 14. Thus, thecontrol system 14 is able to adjust process operating conditions basedon the measured thickness (e.g., based on a generated signature from themeasurement system 16) and the sensed process operating conditions(e.g., based on a signal from the other process sensors). In this way,the control system 14 may selectively refine the seed layer formationprocess 12 to accommodate variations in sensed process conditions andmeasured layer thickness at various stages of the layer formationprocess. For example, the control system 14 may adjust gas flow rates,pressure, temperature, and/or layer formation time (e.g., depositiontime or layer growth time) based on the conditions monitored by themeasurement system 16 and the one or more sensors. As a result, thesystem 10 is capable of achieving substantially uniform seed layercoverage at the sidewall portions of the trench without substantial voidformation and without an increase in process steps to refine theprocess.

According to one aspect of the invention, x-ray reflectometry isemployed to monitor and control the seed layer thickness. X-rayreflectometry is a non-destructive optical technique, which deals withthe measurement and interpretation state of x-rays scattering from asample surface boundary. When x-rays strike a surface at glancingincidence, they can reflect (or scatter) from the surface. However, ifthe surface is rough or covered by a film, then the x-ray reflectivityof a surface can change. X-ray reflectometry takes advantage of thiseffect by measuring the intensity of x-rays reflected from a surface asa function of an angle (referred to as an incident or scattering angle).Total reflection occurs for incident angles smaller than the criticalangle. The critical angle of total reflection is small (e.g., ˜0.2°-1°for a wavelength λ of ˜0.1 nm) and interferences from thin films areonly visible in a small range about the critical angle. Reflectometry issensitive only to electron density and absorption and does not depend oncrystallinity and crystal texture. Reflected intensity (R_(F)) is givenby known Fresnel equations. The reflected intensity may be calculatedusing a recurrence formalism which calculates the reflection coefficientstarting from the lowest surface boundary (e.g., substrate) up to thelast surface boundary (e.g., surface/air). With a recurrence code (e.g.,REFSIM by Siemens or REFS by Bece Scientific) a simulation of x-rayreflectometry spectra can be done. The parameters film thickness,density and roughness may be extracted from the interference spectra,the critical angle and the decrease of the reflectivity as schematicallyshown in FIG. 5. For example, thin films on a surface may give rise tooscillations of the x-ray intensity as a function of the incident angle.

In addition, the characteristic scattering of x-rays from atoms may alsobe done in lattices, referred to as Bragg scattering and exemplified bythe formula nλ=2d sin θ, where n is an integer, λ is the x-raywavelength, d is the spacing between layers (analogous to layerthickness or depth), and θ is often referred to as the Bragg or incidentangle. Bragg scattering gives information about type and changes in acrystal lattice. Scattering x-ray radiation from thin films is somewhatanalogous to scattering radiation at plane parallel plates. However, inthe latter case, special care must be taken since the refractive indexfor all materials is close to 1, and total reflection occurs forincident angles smaller than the critical angle. Total reflection mayalso occur because when dealing with x-rays, it is important to notethat any material is optically thinner than air. Oscillations of x-rayintensity are only visible in a small range around the critical angleθ_(c) (see FIG. 5).

FIG. 2 illustrates an example of an x-ray reflectometry system 40 thatmay be implemented in accordance with the present invention to measurethe thickness of a seed layer 51 (including sidewall portions 52) as itis formed on a barrier layer 54 over a substrate 56. The x-rayreflectometry system 40 includes a measurement system 42 coupled to alight source 44 and a detector 46. The light source 44 may be an x-raytube of polychromatic x-ray radiation. Light beam 48 from the lightsource 44 travels through a collimator 60 and a crystal monochromator62, which is located between the light source 44 and a sample holder(not shown). To switch the measurement to a new spectral region, it isnecessary to rotate the monochromator 62 as well as other elements ofthis system 40 corresponding to a new Bragg angle.

At least a portion of the x-ray beam is reflected, indicated at 50, andreceived at the detector 46. The detector 46 measures the intensity ofthe scattered x-rays through the desired range of incident angles thatpass through an analyzer 66. The analyzer 66 serves to maintain thereflected beams 50 incident upon it with their corresponding spectralregion so that the detector 46 can characterize them. The detector 46 orthe measurement system 42 may then determine x-ray reflectivity as afunction of an incident angle, referred to as θ. One or more signaturesare thus generated corresponding to the scattering angle and x-rayreflectivity. Hence the generated signature corresponds to the thicknessof the seed layer sidewall portions 52 of the seed layer 51.

According to another aspect of the invention, surface roughness σ_(nms)of sidewall portions of a seed layer may be determined using x-rayreflectometry. However, measuring roughness differs slightly frommeasuring thickness. Surface roughness may be calculated by the formula:R_(F) ^(rough)=R_(F) exp(−K_(z) ²σ_(nms) ²), where R_(F) is thereflected intensity and |K_(z)|=2π sin θ/λ. The system 10 (FIG. 1),together with the x-ray reflectometry system 40 (FIG. 2) may be employedas described above to determine surface roughness. However, to obtainvertical surface and interface roughness measurements, the x-rayscattering vector (incident angle) must be perpendicular to the surface.On an x-ray reflectivity spectrum, such as shown in FIG. 5 below,surface roughness may be indicated by a drop in reflectivity(intensity).

FIGS. 3-4 illustrate examples of a system for employing x-rayreflectometry techniques to determine the thickness of seed layer formedon trench sidewalls. FIG. 3 illustrates a system 100 having an x-rayscattering system 102 for in-situ layer thickness monitoring inaccordance with one aspect of the present invention. In this example,the system 100 forms a seed layer 138, such as copper, by chemical vapordeposition (CVD). The seed layer 138 is formed over a barrier layer 136disposed over a substrate 134. The barrier 136 and seed 138 layers areconformal to the trench 139 as well as to the substrate surface. Thebarrier layer 136 may be tantalum nitride or any other metallic nitridefilm. Examples of CVD processes that may be utilized, in accordance withan aspect of the present invention, include Low Pressure CVD (LPCVD),Plasma Vapor Deposition (PVD), and Electrochemical deposition (ECD) suchas electroplating. It is to be appreciated, however, that the presentinvention is applicable to other types of thin film formation, such asother deposition techniques and film growth techniques.

The system 100 includes a process chamber 122 that includes a support,such as a stage 132 (or chuck) operative to support the substrate 134,such as a wafer. A positioning system 126 is operatively connected tothe support 132 for positioning the stage 132 at a desired positionwithin the chamber 122. It is to be appreciated that wafer positioningsystems are rapidly evolving and that any such system may be employed inaccordance with an aspect of the present invention.

A seed layer gas distribution system 114 is operably coupled to thechamber 122 for selectively providing gaseous chemicals into the chamber122 to form the seed layer layer 138 on the substrate 134. By way ofillustration, the gas distribution system 114 includes a source of agaseous medium (a vapor) of seed layer material (e.g., copper) to beformed on the substrate. The gas is provided into the chamber through aconduit that terminates in a nozzle, indicated at 120. While, forpurposes of brevity, a single nozzle 120 is shown in FIG. 3, it is to beappreciated that more than one nozzle or other gas delivery mechanismsmay be utilized to provide gas into the chamber 122 for film formationin accordance with an aspect of the present invention.

The system 100 also may include a load system 124 operatively connectedto the chamber 122 for loading and unloading substrates (e.g., wafers)into and out of the processing chamber 122. The load system 124typically is automated to load and unload the wafers into the chamber122 at a controlled rate. The x-ray scattering system 102, whichcommunicates with the chamber 122, is operative to measure filmthickness in-situ, in accordance with an aspect of the presentinvention. In the example illustrated in FIG. 3, the x-ray scatteringsystem 102 is operative to measure the thickness of the seed layer 138in addition to the thickness of the sidewall portions 140 of the seedlayer 138.

The x-ray scattering system 102 includes a polychromatic light source128, a collimator 125, a monochromator 127, an analyzer 131 and adetector 130. Alternatively, the x-ray scattering system 102 may have acutting slit, a Göbel mirror, an antiscatter slit and a detector slit(all not shown). The x-ray scattering system 102 operates in the samemanner as the x-ray reflectometry system 40 described in FIG. 2. Thepolychromatic light source 128 provides a light beam 142 toward anexposed surface of the barrier layer 136 on which the seed layer 138 andsidewall portions 140 of the seed layer 138 are being formed.Alternatively or in addition, the light beam 142 may be directed at thesidewall portions of the seed layer during and after the seed layer 138,140 has formed on the surface of the barrier layer 136.

The beam 142 interacts with the surface and layer(s) and is reflected.The reflected beam(s) 144, which is received at the detector portion ofthe source/detector 130, has beam properties (e.g., intensity and/orphase), which may be employed to determine an indication of layerthickness. A plurality of incident beams from one or more sources alsomay be directed at different spaced apart locations of the barrier layer136 to obtain corresponding measurements of layer thicknesssubstantially concurrently during the fabrication process. Theconcurrent measurements, in turn, provide an indication of theuniformity of layer thickness across the substrate. By way ofillustration, the intensity of light over a selected wavelength andrange of incident angles varies as a function of layer thickness inx-ray reflectometry.

The x-ray scattering system 102 provides information indicative of themeasured properties to a control system 106. Such information may be theraw phase and intensity information. Alternatively or additionally, thex-ray scattering system 102 may be designed to derive an indication oflayer thickness based on the measured optical properties and provide thecontrol system 106 with a signal indicative of the measured layerthickness according to the detected optical properties. The scattering(incident) angle and intensity of the reflected light can be measuredand plotted in a spectrum.

In order to determine layer thickness, for example, measured signalcharacteristics may be employed to generate a signature corresponding tothe reflectivity intensity over the angle range. The generatedsignatures may be compared with a signal (signature) library of knownsignatures of the same to determine the thickness of the seed layer 138and/or the thickness of the sidewall portions 140 of the seed layer 138.Such substantially unique x-ray reflectivity intensity signatures areproduced by light reflected from and/or refracted by different surfacesdue, at least in part, to the complex index of refraction of the surfaceonto which the light is directed.

The signature library can be constructed from observed intensity/anglesignatures and/or signatures generated by modeling and simulation. Byway of illustration, when exposed to a first incident light of knownintensity, wavelength and angle, a first feature on a wafer can generatea first component of an intensity/angle signature. Similarly, whenexposed to the first incident light of known intensity, wavelength andangle, a second feature on a wafer can generate a second component of aintensity/angle signature. The components can be determined over apredetermined range of incident angles and aggregated to form asignature. For example, a particular type of thin film having a firstthickness may generate a first signature while the same type of filmhaving a different thickness may generate a second signature, which isdifferent from the first signature.

Observed signatures can be combined with simulated and modeledsignatures to form the signature library. Simulation and modeling can beemployed to produce signatures against which measured intensity/anglesignatures can be matched. In one exemplary aspect of the presentinvention, simulation, modeling and observed signatures are stored in asignature library containing, for example, over three hundred thousandintensity/angle signatures. Thus, when the intensity/angle signals arereceived from x-ray scattering detecting components, the intensity/anglesignals can be pattern matched, for example, to the library ofsignatures to determine whether the signals correspond to a storedsignature. Interpolation between the two closest matching signatures maybe employed to discern a more accurate indication of thickness from thesignatures in the signature library. Alternatively, artificialintelligence techniques may be employed to calculate desired parametersof the wafer under test based on the detected optical properties.

The control system 106 includes a processor 110, such as amicroprocessor or CPU, coupled to a memory 108. The processor 110receives measured data from the x-ray scattering system 102. Theprocessor 110 also is operatively coupled to the seed layer material gasdistribution system 114, the positioning system 126 and the load system124. The control system 106 is programmed/and or configured to controland operate the various components within the processing system 100 inorder to carry out the various functions described herein. The processor110 may be any of a plurality of processors, such as the AMD K6®,ATHLON™ or other similar processors. The manner in which the processor110 can be programmed to carry out the functions relating to the presentinvention will be readily apparent to those having ordinary skill in theart based on the description provided herein.

The memory 108 serves to store program code executed by the processor110 for carrying out operating functions of the system as describedherein. The memory 108 may include read only memory (ROM) and randomaccess memory (RAM). The ROM contains among other code the BasicInput-Output System (BIOS) which controls the basic hardware operationsof the system 100. The RAM is the main memory into which the operatingsystem and application programs are loaded. The memory 108 also servesas a storage medium for temporarily storing information such astemperature, temperature tables, position coordinate tables,interferometry information, thickness tables, and algorithms that may beemployed in carrying cut the present invention. The memory 108 also canhold patterns against which observed data can be compared as well asinformation concerning grating sizes, grating shapes, x-rayreflectivity/scattering information, achieved profiles, desired profilesand other data that may be employed in carrying out the presentinvention. For mass data storage, the memory 108 may include a hard diskdrive.

A power supply 116 provides operating power to the system 100. Anysuitable power supply (e.g., battery, line power) may be employed tocarry out the present invention. The system further may include adisplay 104 operatively coupled to the control system 106 for displayinga representation (e.g., graphical and/or text) of one or more processconditions, such as layer thickness, temperature, gas flow rates, etc.The display 104 further may show a graphical and/or textualrepresentation of the measured optical properties (e.g., refractionindex, critical angle, and absorption constant) at various locationsalong the surface of the substrate.

As a result, the system 100 provides for monitoring process conditions,including layer thickness and other sensed process-related conditions,associated with the layer formation process within the chamber 122. Themonitored conditions provide data based on which the control system 106may implement feedback process control in a closed loop so as to form aseed layer 138 having a desired uniform thickness in the sidewallportions 140 of the trench 139 so as to obtain sufficient coverage ofthe trench sidewalls.

FIG. 4 illustrates a plurality of program modules that can reside in amemory 210 employed in the systems illustrated in FIG. 3. The memory 210includes a system control module 220 for controlling the initializationof components in the system, the load system, the positioning system androtation of the chuck. The system control module 220 also operates as akernel for providing a central communication mechanism between the othermodules in the memory 210. A deposition control module 230 providescontrol for enabling and disabling the seed material gas distributionsystem. The measurement control module 240 initializes and controls thex-ray reflectometry system for operating the polychromatic light source,rotation of the monochromator or analyzer and sampling of the detector.A signature generation module 250 aggregates the raw signal samples fromthe x-ray reflectometry system and provides an actual measured signatureof the thickness of the sidewall portions 140 of the seed layer 138(FIG. 3). The signature analysis module 260 searches a signature library270 and compares the actual measured signature(s) with stored signaturesin the signature library 270.

Once a match of the signatures is determined, a corresponding thicknessis determined and passed back to the system control module 220. Thesystem control module 220 then determines if the optimal thickness hasbeen achieved. If the optimal thickness has been achieved, the systemcontrol module 220 notifies the deposition control module 230 toterminate deposition of the material or oxidation of the material.

Turning now to FIG. 5, an exemplary spectrum 300 showing data 310characteristic of the x-ray reflectometry system 102 is illustrated. Thedata 310 corresponds to a multi-layer structure such as, for example, aseed layer over a barrier layer which is formed conformal to a trenchand over a substrate. The spectrum 300 represents reflectivity 320(x-ray intensity) as a function of an incident angle 330. The data 310associated with the spectrum 300 is with respect to the critical angle340 having a 0.5 reflectivity and the wavelength λ being about 0.10 nm.

Interference patterns 360 from thin films are only visible in a smallrange about the critical angle. Thus, as shown in the spectrum 300, theinterference pattern 360 is observed in a small range from the criticalangle 340. According to x-ray reflectometry theory, the film thickness350 for a thin layer such as a barrier layer (over a substrate) can bedetermined by the formula: d≅λ/(2Δθ), where d is the layer thickness, λis the x-ray wavelength, and Δθ is the change in angle. A thin filmlayer (on a substrate) will produce oscillations 350 in the reflectivityrelated to the layer's thickness known as Kiessig fringes 350. As can beseen by the spectrum 300 at oscillations 350, there is little or nochange in the angle θ (at dashed arrows). Therefore, according to theformula, the thickness d will be relatively larger than for the layerrepresented by 360. In addition, rapid oscillations correspond to arelatively thick layer and wider oscillations correspond to a thinnerlayer. Thus, the relatively rapid oscillations 350 in the spectrum 300support the above conclusion.

An interference pattern (beat) is created when more than one layer ispresent, as schematically indicated by 360. That is, the interferencepattern represents the thickness of a layer formed over another layer ona substrate. Here, the interference pattern 360 indicates the thicknessof a second layer such as a seed layer, particularly sidewall portionsof a seed layer. As can be seen by the interference pattern or beat 360,the change in angle Δθ is greater than at the oscillations 350. Thismeans that the sidewall portions of the seed layer are thinner than thebarrier layer. More importantly, actual thickness measurements for thesidewall portions of the seed layer may be ascertained by using theformula d≅λ/(2Δθ) as stated above. Thus, sufficient coverage of the seedlayer over the sidewall portions of the trench can be determined bycalculating the thickness of the seed layer formed on the sidewalls.

In addition to information provided by the oscillations 350 andinterference pattern 360, a drop in intensity (reflectivity), indicatedat 370 and by the angle range 372, illustrates an amount of surfaceroughness. Information related to the surface roughness of a layer mayindicate planarization requirements and/or deficiencies. Surfaceroughness of the seed layer on the sidewall portions of the trench mayor may not adversely affect performance of the subsequently fabricateddevice. However, roughness may be determined in order mitigate deviceerror.

In view of the exemplary systems shown and described above, amethodology, which may be implemented in accordance with the presentinvention, will be better appreciated with reference to the flow diagramof FIG. 6. While, for purposes of simplicity of explanation, themethodology of FIG. 6 is shown and described as executing serially, itis to be understood and appreciated that the present invention is notlimited by the illustrated order, as some blocks may, in accordance withthe present invention, occur in different orders and/or concurrentlywith other blocks from that shown and described herein. Moreover, notall illustrated blocks may be required to implement a methodology inaccordance with the present invention.

Turning now to FIG. 6, the methodology begins at 400 in which asubstrate is positioned within an appropriate environment for desiredprocessing. In this example, the processing is to include formation of abarrier layer over a multi-layer structure, such as, for example, atantalum nitride layer formed conformal to a trench formed in apolysilicon layer over an oxide layer over a silicon substrate. Afterthe substrate is positioned, the process proceeds to 410 in which amulti-layer structure is formed on the substrate. At 420, deposition ofthe seed layer over the multi-layer structure begins. As mentionedabove, seed layer film formation may occur on a barrier layer, such as ametallic nitride film, through a known deposition or film growthtechnique such that the seed layer is conformal to the trench. Theprocess then proceeds to 430. At 430, the thickness of the thin layerbeing formed is measured. By way of example, the layer thickness ismeasured in-situ by an x-ray reflectometry system, although othernon-destructive thickness measuring techniques also could be utilized inaccordance with the present invention. Alternatively or in addition, aprofile of the seed layer formed over the barrier layer, including thesidewall portions may be measured.

From 430, the process proceeds to 440 in which a determination is madeas to whether the measured thickness of the sidewall portions of theseed layer are within expected operating parameters. This determination,for example, may include a comparison of the measured thickness with anexpected (or target) value, such as may be derived based on previousprocesses, calculations using monitored operating conditions within theprocessing chambers, and/or a combination thereof. For example, a signalsignature indicative of reflected and/or refracted light may be comparedrelative to a signature library to provide an indication of thethickness based on its intensity of the reflected and/or refractedlight. If the thickness is within expected operating parameters, theprocess proceeds to 450. At 450, the process terminates the depositionof the seed layer material. If the thickness is not within expectedoperating parameters, the process returns to 420 and continues thedeposition process. Alternatively or in addition, the above processesmay also be performed using a measured profile; in particular, acomparison between a measured profile and a profile signature asdescribed above.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, it is obvious thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described components (assemblies, devices,circuits, etc.), the terms (including any reference to a “means”) usedto describe such components are intended to correspond, unless otherwiseindicated, to any component which performs the specified function of thedescribed component (i.e., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure which performsthe function in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one of several embodiments,such feature may be combined with one or more other features of theother embodiments as may be desired and advantageous for any given orparticular application.

1. A semiconductor processing system, comprising: a processing chamberoperable to form a seed layer conformally over a barrier layer, thebarrier layer formed conformal to a trench and to a substrate located inthe chamber, wherein the trench is formed in the substrate; and an x-rayscattering measurement system for measuring in-situ a thickness of theseed layer at sidewall portions of the trench while the seed layer isbeing formed and for providing a measurement signal indicative of themeasured thickness.
 2. The system of claim 1, further comprising acontrol system for controlling operating characteristics of theformation environment within the chamber, the control system adjustingthe operating characteristics to control formation of the sidewallportions based on the measurement signal.
 3. The system of claim 2,further comprising a seed layer material distribution system operable toconformally deposit seed layer material onto the barrier layer to formthe sidewall portions, the seed layer material distribution system beingcontrolled by the control system.
 4. The system of claim 1, wherein themeasurement system is an x-ray reflectometry system.
 5. The system ofclaim 4, wherein the x-ray reflectometry system includes a polychromaticx-ray light source for generating a spectrum of incident angles at thesidewall portions and a detector to measure an intensity of reflectedx-rays as a function of the incident angles.
 6. The system of claim 5,the detector transmitting the measured intensity of the reflected x-rayswith respect to the incident angles to a control system, the controlsystem being further adapted to generate a signature of the spectrum ofreflectivity as a function of the incident angles that corresponds tothe thickness of the sidewall portions.
 7. The system of claim 6,further comprising a library of signatures corresponding to variousthicknesses of the sidewall portions, the control system being adaptedto search the library for a match to the generated signature todetermine a thickness of the sidewall portions individually.
 8. Thesystem of claim 6, further comprising a library of signaturescorresponding to various profiles of the sidewall portions, the controlsystem being adapted to search the library for a profile match to thegenerated signature to determine a profile and a thickness of thesidewall portions.
 9. The system of claim 6, wherein the control systemcontrols a formation time period during which the sidewall portions areformed, the control system controlling the formation time period basedon the determined thickness.
 10. The system of claim 9, the controlsystem generating a reflectivity signature component and scatteringangle component corresponding to the sidewall portion thickness.
 11. Thesystem of claim 1, further including a display operatively coupled tothe control system and operative to display a visual representation ofthe determined thickness of the sidewall portions during fabrication.12. The system of claim 1, the seed layer being formed of a copper alloysuch as copper-zinc, copper-aluminum, copper-zinc-aluminum,copper-nickel, copper-silver, copper-gold, copper-platinum andcopper-paladium, or a combination thereof.